arch/x86/include/asm/vgtod.h

   1 #ifndef _ASM_X86_VGTOD_H
   2 #define _ASM_X86_VGTOD_H
   3
   4 #include <linux/compiler.h>
   5 #include <linux/clocksource.h>
   6
   7 #ifdef BUILD_VDSO32_64
   8 typedef u64 gtod_long_t;
   9 #else
  10 typedef unsigned long gtod_long_t;
  11 #endif
  12 /*
  13  * vsyscall_gtod_data will be accessed by 32 and 64 bit code at the same time
  14  * so be carefull by modifying this structure.
  15  */
  16 struct vsyscall_gtod_data {
  17         unsigned seq;
  18
  19         int vclock_mode;
  20         cycle_t cycle_last;
  21         cycle_t mask;
  22         u32     mult;
  23         u32     shift;
  24
  25         /* open coded 'struct timespec' */
  26         u64             wall_time_snsec;
  27         gtod_long_t     wall_time_sec;
  28         gtod_long_t     monotonic_time_sec;
  29         u64             monotonic_time_snsec;
  30         gtod_long_t     wall_time_coarse_sec;
  31         gtod_long_t     wall_time_coarse_nsec;
  32         gtod_long_t     monotonic_time_coarse_sec;
  33         gtod_long_t     monotonic_time_coarse_nsec;
  34
  35         int             tz_minuteswest;
  36         int             tz_dsttime;
  37 };
  38 extern struct vsyscall_gtod_data vsyscall_gtod_data;
  39
  40 static inline unsigned gtod_read_begin(const struct vsyscall_gtod_data *s)
  41 {
  42         unsigned ret;
  43
  44 repeat:
  45         ret = ACCESS_ONCE(s->seq);
  46         if (unlikely(ret & 1)) {
  47                 cpu_relax();
  48                 goto repeat;
  49         }
  50         smp_rmb();
  51         return ret;
  52 }
  53
  54 static inline int gtod_read_retry(const struct vsyscall_gtod_data *s,
  55                                         unsigned start)
  56 {
  57         smp_rmb();
  58         return unlikely(s->seq != start);
  59 }
  60
  61 static inline void gtod_write_begin(struct vsyscall_gtod_data *s)
  62 {
  63         ++s->seq;
  64         smp_wmb();
  65 }
  66
  67 static inline void gtod_write_end(struct vsyscall_gtod_data *s)
  68 {
  69         smp_wmb();
  70         ++s->seq;
  71 }
  72
  73 #ifdef CONFIG_X86_64
  74
  75 #define VGETCPU_CPU_MASK 0xfff
  76
  77 static inline unsigned int __getcpu(void)
  78 {
  79         unsigned int p;
  80
  81         /*
  82          * Load per CPU data from GDT.  LSL is faster than RDTSCP and
  83          * works on all CPUs.  This is volatile so that it orders
  84          * correctly wrt barrier() and to keep gcc from cleverly
  85          * hoisting it out of the calling function.
  86          */
  87         asm volatile ("lsl %1,%0" : "=r" (p) : "r" (__PER_CPU_SEG));
  88
  89         return p;
  90 }
  91
  92 #endif /* CONFIG_X86_64 */
  93
  94 #endif /* _ASM_X86_VGTOD_H */